package com.lagou.sqlsesstion;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;


import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> Object query(Configuration configuration, MappedStatement statement, Object... params) {

        //获取Connection
        Connection connection;
        try {
            connection = configuration.getDataSource().getConnection();
            //获取sql语句
            String sqlText = statement.getSql();


            BoundSql boundSql = getBoundSql(sqlText);

            // 3.获取预处理对象：preparedStatement
            PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

            // 4. 设置参数
            //获取到了参数的全路径
            String paramterType = statement.getParameterType();
            Class<?> paramtertypeClass = getClassType(paramterType);

            List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
            for (int i = 0; i < parameterMappingList.size(); i++) {
                ParameterMapping parameterMapping = parameterMappingList.get(i);
                String content = parameterMapping.getContent();

                //反射
                Field declaredField = paramtertypeClass.getDeclaredField(content);
                //暴力访问
                declaredField.setAccessible(true);
                Object o = declaredField.get(params[0]);

                preparedStatement.setObject(i + 1, o);

            }


            // 5. 执行sql
            Integer resultSet = preparedStatement.executeUpdate();
//            String resultType = statement.getResultType();
//            Class<?> resultTypeClass = getClassType(resultType);
//
//            ArrayList<Object> objects = new ArrayList<>();
//
//            // 6. 封装返回结果集
//            while (resultSet.next()) {
//                Object o = resultTypeClass.newInstance();
//                //元数据
//                ResultSetMetaData metaData = resultSet.getMetaData();
//                for (int i = 1; i <= metaData.getColumnCount(); i++) {
//
//                    // 字段名
//                    String columnName = metaData.getColumnName(i);
//                    // 字段的值
//                    Object value = resultSet.getObject(columnName);
//
//                    //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
//                    PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
//                    Method writeMethod = propertyDescriptor.getWriteMethod();
//                    writeMethod.invoke(o, value);
//
//
//                }
//                objects.add(o);
//
//            }

            return resultSet;

        } catch (Exception e) {
            return null;
        }
    }

    /**
     * @param sql
     * @return
     * @desc 将# {} 使用? 代替
     */
    private BoundSql getBoundSql(String sql) {

        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;

    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType != null) {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;

    }
}
